Rate

40-60

Regularity

Regular

P waves

Inverted, if present

PRI

< 0.12, if P waves are even visible

QRS

0.08-0.12

Rate

160-240

Regularity

Regular or irregular

P waves

Bizarre/unusual

PRI

< 0.20

QRS

0.08-0.12

Rate

40-100

Regularity

Regular

P waves

None

PRI

None

QRS

> 0.12; bizarre